Various retrieval devices may be used to remove a targeted object (e.g., a kidney stone) from a portion of a body (e.g., the interior portion of a kidney). Some retrieval devices may include a flexible sheath configured for delivery through a working channel of an insertion device, and an end effector deployable from a lumen of the flexible sheath. Exemplary insertion devices may include an endoscope or a ureteroscope; and exemplary end effectors may include an expandable basket. Some end effectors may include a wire extending through the lumen of the sheath, and an expandable basket attached to a distal end of the wire. The basket may be closed into a the lumen when the sheath is moved distally relative to the wire, and opened out the lumen when the sheath is moved proximally. Over time, these reciprocal movements may cause damage to the device or otherwise complicate the stone retrieval process. For example, the end effector may break or otherwise be damaged if too much movement force is applied to the sheath. Even with normal movement forces, sheath compression may occur, wherein the sheath becomes shorter over time unit it cannot extend distally to close the end effector entirely, making it difficult to capture smaller stones.
The risk of damage and/or malfunction from reciprocal movements increases when the sheath is placed in a tortuous path. For example, the sheath may be snaked through a body path including curves and/or twists, such as a path extending from the urethra, through the bladder and ureter, around the renal pelvis, and into or out of a particular calyx of a kidney. Such a path may shift the lumen relative to the wire, causing the wire to hug the inner radius of curved portions of the lumen of the sheath, and lengthening the wire relative to the sheath. The resulting mismatch or offset in the sheath and wire lengths may prevent the end effector from closing completely, again making it difficult to capture smaller stones.
The devices and methods disclosed herein may remedy one or more of the aforementioned difficulties of capturing smaller stones, and/or address other aspects of the prior art.